Solution:First Premise is Particular Affirmative (I-type).Second and third Premises are Universal Affirmative (A- type).
Some tablets are rains.

All rains are chairs.
We know that,
I + A ⟹ I - type Conclusion Thus, our derived Conclusion would be :
'Some tablets are chairs'.
This is the Conclusion IV.
Conclusion I is the Converse of this Conclusion.
All dogs are rains.

All rains are chairs.
We know that,
A + A ⟹ A-type Conclusion Thus, our derived Conclusion would be :
'All dogs are chairs'.
Thus is the Conclusion II.
Some rains are dogs.(Converse of Second Premise)

All dogs are chairs.
We know that,
I + A ⟹ I-type Conclusion Thus, our derived Conclusion would be :
"Some rains are chairs".
Thus, Conclusions I, II and IV follow.